The present invention relates to an apparatus and method that are useful in the measurement of the pressure within the human body abdominal cavity or hollow viscous organ contained in the abdominal cavity. More specifically, the present invention relates to an apparatus and method that utilizes the patient""s own bodily fluid collected within a reservoir to measure the intra-abdominal pressure.
The measurement of intra-abdominal (or intra-visceral) pressure is routinely made in the clinical management of critically ill patients, or patients undergoing major surgery. Typically, the urinary bladder is the preferred site for the pressure measurement, but other hollow organs, such as the stomach, may be used as well.
Urinary bladder pressure is presently measured by connecting a pressure recording device to the patient""s urinary (Foley) catheter, which empties the bladder into a drainage container. Under the prior art method, the drainage container tube is clamped and 50 cc of sterile saline is infused into the bladder from a syringe by a needle inserted into the catheter""s sampling port. After infusion, the pressure in the bladder is recorded using the level of the pubic bone (symphysis pubis) as the zero pressure reference. This method is both time-consuming and presents a risk for bladder infection because the closed sterile tubing may be contaminated by the introduction of the needle when inserting the supply of saline.
The present invention relates to a method and apparatus for determining the intra-abdominal pressure of a patient. Specifically, the present invention relates to an apparatus and method that utilizes a stored quantity of the patient""s own bodily fluid to determine the intra-abdominal pressure within the patient.
In the first embodiment of the invention, the pressure measuring apparatus includes a fluid reservoir that is positioned between a urinary catheter inserted into the patient and the collection container for urine withdrawn from the patient through the urinary catheter. The reservoir has a predetermined internal volume that stores a predetermined amount of urine within the reservoir. An outlet opening within the reservoir allows excess urine to drain into the collection chamber. The reservoir is connected to the urinary catheter by a manometer tube having a series of indicator marks, including a zero marking.
During pressure determination, the reservoir is elevated to a measurement height above the patient until the zero marking on the manometer tube is generally level with the pubic bone of the patient. A filtered air vent at the top of the reservoir provides atmospheric pressure inside of the reservoir. As the reservoir is elevated to the measurement height, the internal supply of the patient""s own urine within the reservoir flows through the manometer tube and the urinary catheter back into the bladder of the patient. Once the reservoir has been elevated such that the zero marking on the manometer tube is level with the pubic bone, the height of the liquid column contained within the manometer tube provides a direct indication of the intra-abdominal pressure of the patient.
Alternatively, the manometer tube extending between the reservoir and the urinary catheter can be replaced by a simple, unmarked transparent inlet tube extending between the reservoir and the urinary catheter. A measuring tape including a series of indicator marks is attached to the bottom of the reservoir and the opposite end of the measuring tape is fixed relative to the patient""s bed. The length of the measuring tape is fixed such that a zero marking on the measuring tape corresponds to the level of the patient""s pubic bone when the patient is in a supine position. The measurement height of the reservoir is thus dictated by the length of the measuring tape. When the reservoir is at its prescribed measurement height, the height of the liquid column within the transparent inlet tube is measured along the indicator lines on the measuring tape. The height of the liquid column directly measures the intra-abdominal pressure of the patient.
In a second embodiment of the invention, the reservoir is positioned between a naso-gastric tube and a supply of suction used to withdraw fluid from a patient""s stomach. During normal draining situations, the reservoir is in an inverted position that allows suction to withdraw fluid from the patient""s stomach. A ball within the reservoir closes the air vent to the reservoir when the reservoir is in its inverted position.
Measurement of the patient""s intra-abdominal pressure through the naso-gastric tube is done by first placing the reservoir in an upright position. In the upright position, the ball within the reservoir closes the outlet opening to the supply of suction to prevent the patient""s stored stomach fluid from leaving the reservoir through the suction tube while allowing air to enter the reservoir through the filtered vent. The reservoir is then elevated in the manner described previously such that the patient""s own stomach fluid flows back into the patient""s stomach.. The height of the stored stomach fluid within the manometer tube provides a direct indication of the intra-abdominal pressure of the patient.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.